In the so-called direct synthesis reaction, a process in which silicon powder is reacted with methyl chloride in the presence of a copper catalyst, other silanes are obtained in addition to the main product dimethyldichlorosilane. For example, dimethylchlorosilane is obtained, but only in low yields.
The redistribution of two silanes having Si-bonded methyl groups, hydrogen atoms and/or chlorine atoms in the presence of quaternary ammonium salts is disclosed in K. Moedritzer et al., Journal of Organometallic Chemistry 12 (1968) 69-77.
According to U.S. Pat. No. 3,399,222 (issued Aug. 27, 1968, D. R. Weyenberg et al., Dow Corning Corp.), in the redistribution reaction of dimethyldichlorosilane with methyldichlorosilane in the presence of quaternary ammonium salts, the following equilibrium is on the left hand side: EQU (CH.sub.3).sub.2 SiCl.sub.2 +CH.sub.3 HSiCl.sub.2 .revreaction.(CH.sub.3).sub.2 SiCl+CH.sub.3 HSiCl.sub.3
In U.S. 4,870,200 (issued Sep. 26, 1989, R. Ottlinger et al., Wacker-Chemie GmbH) the disproportionation of methyldichlorosilane to form methylchlorosilane and/or methylsilane in the presence of a catalyst, composed of a support which is insoluble in the reaction medium and to which tertiary, amine groups or quaternary ammonium groups are covalently bonded, is described.
It is an object of the present invention to provide a process for the preparation of dimethylchlorosilane by the redistribution reaction of dimethyldichlorosilane with at least one silane having Si-bonded methyl groups, hydrogen atoms and/or chlorine atoms in the presence of a catalyst. Another object of the present invention is to provide a process which produces good yields of dimethylchlorosilane. A further object of the present invention is to provide a process in which the redistribution reaction proceeds in the presence of heterogeneous catalysts. A further object of the present invention is to provide a process in which the catalyst can easily be removed from the reaction mixture and recovered. A still further object of the present invention is to provide a continuous process for preparing dimethylchlorosilane.